This invention relates to a mixture for preparation of protective and insulating coatings on metals and on metal products. Such mixtures are applied in the form of powder or paste and are resistant to high temperature and have good electrical properties. The present invention relates particularly to the application of insulating materials on metal bearing plates covered by insulating material in hybrid electronics.
Protective and insulating coatings are applied on metals in different ways, for example by application of different varnishes or suitable enamels and the like. Enamels applied on steel sheets are resistant to higher temperatures and are therefore used for preparation of bearing plates in hybrid electronics for printed circuits and for resistors, which can be subsequently burnt at maximum temperatures of 675.degree. C. Actual electronic circuits, however, require not only burning of insulating metal bearing plates at high temperatures but also require effective heat removal from power loaded electronic parts. A good electrical insulation of active electronic elements from metal parts together with good heat removal is also frequently required. These requirements can be met by application of beryllium ceramics either as bearing plates for electronic hybrid circuits or as insulating means between an active power loaded element and a metal part securing heat removal. A drawback of beryllium ceramics is its high cost and the occupational health hazard due to its high toxicity.